Urinary retention rates after intravesical onabotulinumtoxinA injection for idiopathic overactive bladder in clinical practice and predictors of this outcome.

Aims: The purpose of this study was to find the rate of urinary retention in clinical practice after treatment with onabotulinumtoxinA (BTN/A) for refractory overactive bladder (OAB) symptoms and determine factors that predict this outcome.

Methods: This is a retrospective study of BTN/A for treatment of non-neurogenic, refractory OAB symptoms. Patients were analyzed with respect to their first and second BTN/A injections. The primary outcome measure was postoperative urinary retention. Statistical significance was assessed with multivariate logistic regression.

Results: Based on inclusion and exclusion criteria, the study population was 160. Mean age was 64 ± 13.2 years and 24% of the patients were men. The rate of urinary retention was 35% (n = 56). For the first BTN/A treatment, multivariate analysis revealed that preoperative PVR (post-void residual volume) (OR 1.27, 95% CI 1.13-1.43, P < 0.001) and preoperative bladder capacity (OR 1.05, 95% CI 1.01-1.08, P = 0.005) were associated with postoperative urinary retention. In patients with a preoperative PVR of ≥100 ml, 94% (n = 17) went into urinary retention. For those who underwent a second BTN/A treatment, preoperative PVR, BTN/A units injected and retention after the first BTN/A were associated with an increased rate of postoperative retention.

Conclusions: Increased preoperative PVR was associated with urinary retention. The retention rate is higher than that reported in recent clinical trials. The inclusion of patients with a preoperative PVR ≥100 ml and a lower threshold to initiate clean intermittent catheterization contributed to this high rate of retention.